1. Field of the Invention
The present disclosure relates to a phenylphenoxazine or phenylphenothiazine-based compound and an organic electroluminescent device comprising the same.
2. Description of the Related Art
Organic electroluminescent devices are self-emissive display devices that emit light generated by the recombination of electron and holes in a fluorescent or phosphorescent organic compound thin layer (hereinafter, referred to as an organic layer) when a current is provided to the organic layer. Organic electroluminescent devices have only a few components and thus can be manufactured to be light in weight, using simple manufacturing processes. In addition, organic electroluminescent devices produce high quality images and have wide viewing angles. Furthermore, organic electroluminescent devices can be used in mobile devices to provide images of high quality, and high color purity, at low levels of electric power and at low operation voltages. Due to these and other advantages, organic electroluminescent devices have electrical properties suitable for use in portable electronic devices.
Eastman Kodak Co. in U.S. Pat. No. 4,885,211 has disclosed an organic electroluminescent device having a multi-layer structure comprising an aluminum quinolinol complex layer and a triphenylamine derivative layer. U.S. Pat. No. 5,151,629 discloses that the use of a low molecular weight molecule for an organic emission layer enables a wider emission range from an ultraviolet light region to an infrared light region.
Light-emitting devices are self-emissive devices. Light-emitting devices have wide viewing angles, excellent contrast properties, and quick response speeds. Light-emitting devices can be categorized into inorganic light emitting devices comprising an emission layer formed of an inorganic compound, and organic light emitting devices (OLED) comprising an emission layer formed of an organic material. OLEDs have better brightness, smaller operation voltages, and quicker response speeds than inorganic light emitting devices. In addition, OLEDs can provide various colors. Due to these advantages of OLEDs, extensive research into the development and use of OLEDs is currently being performed.
In general, OLEDs have a basic stack structure comprising an anode an organic emission layer, and a cathode. In addition, OLEDs can have other various structures. Examples of such stack structures include an anode/a hole injection layer/a hole transport layer/an emission layer/an electron transport layer/an electron injection layer/a cathode, or an anode/a hole injection layer/a hole transport layer/an emission layer/a hole blocking layer/an electron transport layer/an electron injection layer/a cathode.
In cases where an organic electroluminescent device is used in a display device, low levels of power consumption can be obtained when the same emission efficiency is obtained under a low operating voltage, or when a high emission efficiency is obtained under the same operating voltage.
U.S. Pat. No. 4,356,429 discloses a phthalocyanine compound, such as copper phthalocyanine, for use as a hole-injecting material. Advanced Materials, vol. 6, p. 677 (1994) also discloses star-burst amine derivatives, such as 4,4′,4″-tri(N-carbazolyl)triphenylamine (TCTA), 4,4′,4″-tris[N,N-(m-tolyl)phenylamino]triphenylamine (m-MTDATA), or 1,3,5-tris[4-(3-methylphenylphenylamino)phenyl]benzene (m-MTDAPB), for use as hole injecting materials. The use of these compounds as hole-injecting materials decreases the operating voltage of the organic electroluminescent device. However, in each of these cases, sufficient lifetime, efficiency, and electrical power consumption cannot be obtained.
A material disclosed in U.S. Pat. No. 6,541,129 shows excellent organic electroluminescent properties as compared to prior art materials, but does not show sufficient thermal stability due to its low glass transition temperature.